Wireless communication terminal

ABSTRACT

In one implementation, an antenna array has a plurality of antenna element, each of which is configured to apply a phase shift to a signal. A beam steering controller is configured to steer a main beam of the antenna by controlling the phase shifts applied by the antenna elements. In addition, the beam steering controller also is configured to detect a failure of an antenna element and, in response to detecting the failure, disable the failed antenna element and modify the phase shifts applied by remaining ones of the antenna elements.

TECHNICAL FIELD

The disclosure relates generally to a wireless communication terminal.

SUMMARY

According to one implementation of the disclosure, an antenna array hasa plurality of antenna elements, each of which is configured to apply aphase shift to a signal transmitted by the antenna element. A beamsteering controller is configured to steer a main beam of the antenna bycontrolling the phase shifts applied by the antenna elements. Inaddition, the beam steering controller is also configured to detect afailure of an antenna element and, in response to detecting the failure,disable the failed antenna element and modify the phase shifts appliedby remaining ones of the antenna elements.

According to another implementation of the disclosure, the phase shiftsapplied by individual ones of the antenna elements of a phased arrayantenna are controlled to steer a main beam of the antenna in adirection, a determination that one of the antenna elements has failedis made, and, in response, the failed antenna element is disabled andthe phase shifts applied by remaining ones of the antenna elements aremodified to steer the main beam of the antenna effectively in the samedirection.

According to yet another implementation of the disclosure, a wirelesscommunications terminal includes a phased array antenna that hasmultiple antenna elements and memory storing multiple different beampointing data structures. Each beam pointing data structure correspondsto a particular combination of enabled and disabled antenna elements ofthe antenna and stores values that represent phase shifts to be appliedby individual ones of the enabled antenna elements for the particularcombination to steer the main beam of the antenna in a number ofdifferent predetermined directions. The wireless communication terminalalso includes a beam steering controller configured to determine acurrent combination of enabled and disabled antenna elements, select abeam pointing data structure from among the multiple different beampointing data structures that corresponds to the current combination ofenabled and disabled antenna elements, and control phase shifts appliedby the currently enabled antenna elements to steer the main beam of theantenna using phase shifts represented in the selected beam pointingdata structure.

Other features of the present disclosure will be apparent in view of thefollowing detailed description of the disclosure and the accompanyingdrawings. Implementations described herein, including theabove-described implementations, may include a method or process, asystem, or computer-readable program code embodied on computer-readablemedia.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the present disclosure, referencenow is made to the following description taken in connection with theaccompanying drawings.

FIG. 1 is a block diagram of a system for wireless communication inaccordance with a non-limiting implementation of the present disclosure.

FIG. 2 is a flow chart of a method for operating an antenna array inaccordance with a non-limiting implementation of the present disclosure.

FIG. 3 is a block diagram of a wireless communication terminal inaccordance with a non-limiting implementation of the present disclosure.

FIG. 4 is a block diagram of an antenna element from a wirelesscommunication terminal in accordance with a non-limiting implementationof the present disclosure.

FIG. 5 is a block diagram of a beam steering controller from a wirelesscommunication terminal in accordance with a non-limiting implementationof the present disclosure.

DETAILED DESCRIPTION

Certain satellite wireless communication systems include terminals(e.g., mobile terminals) that use switched beam antenna arrays tocommunicate with one or more satellites. Such switched beam antennaarrays may couple a group of active antennas, or antenna elements, toproduce a directional radiation pattern that enables the terminal tofocus transmission and/or reception of signals in fairly specificdirections for communicating with one or more target satellites. Aswitched beam antenna array may be configured to provide severalpredefined beam patterns, enabling the terminal to select a particularbeam from among the predetermined patterns to use at any given point intime (e.g., depending on the relative position of a satellite with whichthe terminal is communicating).

In certain implementations, each antenna element may include atransmit/receive module having a power amplifier (e.g., for amplifyingsignals to be transmitted) and a low-noise amplifier (e.g., foramplifying received signals). If an individual antenna element fails(e.g., the antenna element's transmit/receive module fails due to damageto its power amplifier and/or low noise amplifier), the terminal maydisable the failed antenna element and intelligently reconfigure itselfto continue operation with the failed antenna element disabled. Forexample, as described in greater detail below, the terminal mayreconfigure the different phase shift values to be applied by theindividual antenna elements to enable the switched beam antenna array tocontinue to offer substantially the same radiation patterns as beforethe failure of the antenna element or to offer a new set of radiationpatterns that are perceived as advantageous in view of the remainingoperational antenna elements. Additionally or alternatively, theterminal may change the modulation scheme (e.g., from 16 amplitude andphase-shift keying (“16APSK”) to 8 phase-shift keying (“8PSK”) or from8PSK to quadrature phase-shift keying (“QPSK”)) used to communicate witha target satellite as appropriate to compensate for the decrease in gaincaused by the failure of the antenna element.

Referring to FIG. 1, a system 100 for wireless communication isillustrated in accordance with a non-limiting implementation of thepresent disclosure. System 100 includes wireless communication devices30 each having an antenna array 32 (e.g., a phased array antenna) thatincludes antenna elements 32 a-m. Devices 30 communicate in a wirelesscommunication network that includes cross-linked satellites 10, groundstation 50, external network 60 and device 70. For example, devices 30may be mobile satellite communication terminals mounted on ships and/oraircraft to enable crew, passengers, or equipment on board to engage inwireless communications with remote systems (e.g., via network 60 and/ordevice 70) and/or other forms of mobile satellite communication devicesincluding satellite telephones/handsets. Devices 30 are configured tocommunicate with (e.g., transmit signals to and/or receive signals from)satellites 10. Communication signals transmitted from devices 30 to asatellite 10 are relayed from the satellite 10 to ground station 50(e.g., directly or via satellite crosslinks) and on to a destinationsuch as device 70 or an external network 60. Similarly, communicationsignals from network 60 or device 70 destined for one of devices 30 maybe relayed from ground station 50 through one or more satellites 10 tothe intended device 30.

Each antenna element 32 a-m in a device 30 may include an individualantenna 33 a-m and a transmit/receive module 34 a-m that includes one ormore of a phase shifter, a power amplifier (e.g., for amplifying outputsignals), and a low-noise amplifier (e.g., for amplifying receivedsignals). Each device 30 also may include a beam steering controller(“BSC”) 36 to steer the main beam(s) of the antenna array 32, forexample by controlling the phase shifters of the transmit/receivemodules 34 a-m. In certain implementations, the BSC 36 may includememory 38 (e.g., non-volatile memory such as flash, read-only memory(“ROM”), programmable read-only memory (“PROM”), erasable programmableread-only memory (“EPROM”), and electrically erasable programmableread-only memory (“EEPROM”) and/or volatile memory such as dynamicrandom access memory (“DRAM”) and static random access memory (“SRAM”)),and a processor 40. The BSC 36 also may include one or more beampointing tables (“BPTs”) 47 or similar data structures that store thedifferent phase shift values (e.g., complex weights) to be applied bytransmit/receive modules 34 a-m to achieve each of the predeterminedradiation patterns (e.g., predetermined directions of the main beam(s))of the antenna array 32. In certain implementations, BPTs 47 may beimplemented in memory 38.

Each device 30 may be configured to continue to enable communicationswith satellites 10 even if one or more of the antenna elements 32 a-m ofantenna array 32 fails or otherwise is disabled (e.g., due to damage toone or more of the power amplifier, low noise amplifier, the antenna,etc.). For example, BSC 36 may include multiple different BPTs 47corresponding to different operational states of antenna array 32enabling BSC 36 to continue to steer the main beam(s) of antenna array32 even when one or more antenna elements 32 a-m fail. Moreparticularly, BSC 36 may include an individual BPT 47 for every possiblecombination (or each of some subset of possible combinations) of enabledand disabled antenna elements 32 a-m of antenna array 32 and, when anantenna element fails, that antenna element may be disabled and BSC 36may use the particular BPT 47 that corresponds to the currentcombination of enabled and disabled antenna elements to steer the mainbeam(s) of the antenna array 32.

Additionally or alternatively, device 30 also may be configured toswitch the modulation scheme used to communicate with a satellite 10 toaccommodate the loss in gain attributable to the failure of one or moreantenna elements 32 a-m. For example, the satellites 10 and device 30may be capable of communicating using multiple different signalconstellations, such as, for example, 16APSK, 8PSK, and QPSK, and device30 may switch from a first signal constellation (e.g., 16APSK) to asecond signal constellation that requires a lower signal-to-noise(“SNR”) ratio (e.g., 8PSK) responsive to detecting that one or moreantenna elements 32 a-m failed to accommodate the lower gain availabledue to the failure of the antenna element(s) 32 a-m.

Referring to FIG. 2, a method 200 for operating an antenna array (e.g.,a phased array antenna) having multiple antenna elements is illustratedin accordance with a non-limiting implementation of the presentdisclosure. At step 210, failure of one of the antenna elements isdetected. In certain implementations, failure of the antenna of theantenna element may be detected. Additionally or alternatively, failureof a power amplifier or other component in the antenna element, such as,for example, a low noise amplifier, an RF switch, etc. may be detected.For example, in order to detect the operational state of a poweramplifier, in certain implementations, a power sensor may be coupled tothe output of the power amplifier (e.g., using a low level coupler). Ifthe power sensor (operating independently or in connection withadditional logic circuitry) determines that the power in a signal outputby the power amplifier is below (or has fallen below) a predeterminedthreshold value, a determination may be made that the power amplifierhas failed. Similarly, in order to detect the operational state of a lownoise amplifier, in certain implementations, a power sensor may becoupled to the output of the low noise amplifier (e.g., using a lowlevel coupler). If the power sensor (operating independently or inconnection with additional logic circuitry) determines that the power ina signal output by the low noise amplifier is below (or has fallenbelow) a predetermined threshold value, a determination may be made thatthe low noise amplifier has failed. In certain implementations, similarcomponents and techniques may be employed to detect the failure of othercomponents of an antenna element.

At step 220, the failed antenna element is disabled (or at leastpartially disabled). In certain implementations, the antenna element maybe disabled by applying a predefined impedance to the antenna element.In certain implementations, if the detected failure relates to thefailure of the power amplifier of the antenna element, the failed poweramplifier is disabled. In such implementation, the antenna element maybe disabled from operating in a transmit mode but still may be capableof operating in a receive mode. Thus, the failed antenna element may besaid to be only partially disabled.

At step 230, the phase shifts applied by the remaining enabled antennaelements are modified to accommodate the failed antenna element. Forexample, when the failed antenna element is disabled, the phase shiftsapplied by the remaining enabled antenna elements may be adjusted inorder to maintain the main beam of the antenna in substantially the samedirection as it was prior to the failure of the antenna element.

In certain implementations, the phase shifts to be applied by individualantenna elements to steer one or more main beams of the antenna in anumber of predetermined directions may be stored in memory in one ormore beam pointing tables or similar data structures. The beam pointingtable(s) may store phase shift values (or representations of phase shiftvalues) to be applied by individual antenna elements to steer the mainbeam(s) of the antenna in a number of predetermined directions for eachpossible combination of enabled and disabled antenna elements in theantenna array. When an antenna element failure is detected, the failedantenna element may be disabled and the current combination of enabledand disabled antenna elements may be determined. A particular beampointing table then may be selected based on the current combination ofenabled and disabled antenna elements. The selected beam pointing tablemay store phase shift values (or representations of phase shift values)to be applied by each of the remaining enabled antenna elements to steerthe main beam(s) of the antenna in a number of predetermined directions.

In implementations in which a failed antenna element is disabled fromoperating in the transmit mode but remains capable of operating in thereceive mode, different beam pointing tables may be selected dependingon whether the antenna is transmitting a signal or receiving a signal.In particular, a beam pointing table that corresponds to the currentcombination of enabled and disabled antenna elements for operating inthe transmit mode may be selected when the antenna is transmitting asignal and a different beam pointing table that corresponds to thecurrent combination of enabled and disabled antenna elements foroperating in the receive mode may be selected when the antenna isreceiving a signal.

Additionally or alternatively, in certain implementations in which thephase shifts to be applied by individual antenna elements are stored inmemory in one or more beam pointing tables or similar data structures, afirst set of beam pointing tables or similar data structures may storephase shift values (or representations of phase shift values) to beapplied by individual antenna elements for each possible combination ofenabled and disabled antenna elements in the antenna array when theantenna is operating in the transmit mode and a second set of beampointing tables or similar data structures may store phase shift values(or representations of phase shift values) to be applied by individualantenna elements for each possible combination of enabled and disabledantenna elements in the antenna array when the antenna is operating inthe receive mode. In such implementations, an appropriate beam pointingtable or similar data structure will be selected from among the firstset or second set depending on whether the antenna is transmitting asignal or receiving a signal.

In certain implementations, a BSC may control the phase shifts appliedby the remaining enabled antenna elements according to the selected beampointing table.

With reference to FIG. 3, a wireless communication terminal 300 isillustrated in accordance with a non-limiting implementation of thepresent disclosure. Wireless communication terminal 300 may correspondto one of devices 30 illustrated in FIG. 1.

An antenna array (e.g., a phased array antenna) has antenna elements 312a-m, each of which includes a transmit/receive module 310 a-m and anantenna 311 a-m. Each transmit receive module 310 a-m is connected to aradio-frequency (“RF”) summing junction 314 which is connected to amodem 318.

When the wireless communication terminal 300 is receiving, variants of asignal (e.g., phase-shifted variants) are received by the antennas 311a-m of the antenna elements 312 a-m and then processed by thecorresponding transmit/receive modules 310 a-m of the antenna elements312 a-m. For example, the transmit/receive modules 310 a-m may applyphase shifts to the received variants of the signal. Thetransmit/receive modules 310 a-m also may amplify the received variantsof the signal (e.g., using low noise amplifiers incorporated within thetransmit/receive modules 310 a-m). The processed signals then arecombined by the RF summing junction 314 and the resultant signal istransmitted to the modem 318 for further processing (e.g., demodulation)and use by the wireless communication terminal.

When the wireless communication terminal 300 is transmitting, the signalto be transmitted is modulated by modem 318 and then transmitted to theRF summing junction 314. The RF summing junction splits the signal andtransmits it to the transmit/receive modules 310 a-m of the antennaelements 312 a-m. The transmit/receive modules 310 a-m of the antennaelements 312 a-m then process the signals before they are transmitted bythe corresponding antennas 311 a-m of the antenna elements 312 a-m. Forexample, the transmit/receive modules 310 a-m may apply phase sifts tothe signals. The transmit/receive modules 310 a-m also may amplify thesignals (e.g., using power amplifiers incorporated within thetransmit/receive modules 310 a-m).

A BSC 316 is connected to each transmit/receive module 310 a-m as wellas modem 318. BSC 316 may control the phase shifts applied by eachtransmit/receive module 310 a-m to steer the main beam(s) of the antennaarray in a number of predetermined directions. The BSC 316 may receiveinput from modem 318 (e.g., based on signals received by the wirelesscommunication terminal) that guides the BSC's 316 selection of thedirection in which to steer the main beam(s) of the antenna array at aparticular point in time.

With reference to FIG. 4, an antenna element 400 from a wirelesscommunication terminal having an antenna array (e.g., a phased arrayantenna) is illustrated in accordance with a non-limiting implementationof the present disclosure. Antenna element 400 may correspond to one ofthe antenna elements 32 a-m illustrated in FIG. 1 or one of the antennaelements 312 a-m illustrated in FIG. 3.

Antenna element 400 includes a transmit/receive module 410 and anantenna 412. Transmit/receive module 410 includes an enable/disableswitch 420, a band pass filter (“BPF”) 424, transmit/receive switches426 and 432, a low noise amplifier 428, a power amplifier 430, a phaseshifter 434, and a controller 436. In addition, transmit/receive module410 is connected to a BSC (not shown) and an RF summing junction (notshown). In some implementations, controller 436 may be implemented as afield programmable gate array (FPGA). Alternatively, in otherimplementations, controller 436 may be implemented as a microprocessor.

Enable/disable switch 420 may be configured to enable antenna element400 to be switched from being enabled to transmit and/or receive signalsto disabled from transmitting and/or receiving signals (e.g., inresponse to detection of a failure of antenna element 400 or one of itscomponents) and vice versa. Enable/disable switch 420 is controlled bycontroller 436. When the antenna element 400 is enabled, controller 436controls enable/disable switch 420 to provide a signal path betweenantenna 412 and phase shifter 434, thereby enabling antenna element 400to transmit and/or receive signals. In contrast, when the antennaelement 400 is disabled, controller 436 controls enable/disable switch420 to switch so that a known impedance 422 a and 422 b is applied toboth the antenna 412 and the transmit/receive module 410, therebydisabling antenna element 400 from transmitting and/or receivingsignals. In some implementations, enable/disable switch 420 may be amechanical switch. Alternatively, in other implementations,enable/disable switch 420 may be an electronic switch.

Antenna element 400 is configured to operate in one or both of atransmit mode and a receive mode. When operated in the transmit mode,antenna element 400 transmits a signal and, when operated in the receivemode, antenna element 400 receives a signal. Transmit/receive switches426 and 432 (which, for example, may be implemented as mechanical orelectronic switches) enable transmit/receive module 400 to switchbetween operating in the transmit mode and the receive mode and arecontrolled by signals received from controller 436.

When transmit/receive module 410 is operated in the transmit mode,controller 436 (which itself may be controlled by the BSC) causestransmit/receive switches 426 and 432 to switch to provide a signal pathfrom the RF summing junction to antenna 412 through phase shifter 434,power amplifier 430, and BPF 424. Phase shifter 434 applies a phaseshift to the signal received from the RF summing junction. After thephase shift has been applied to the signal, power amplifier 430amplifies the signal. Finally, BPF 424 filters out components of theamplified signal that are outside of the frequency band(s) in whichantenna element 400 is configured to transmit signals before the signalis passed to antenna 412 and transmitted. In certain implementations,BPF 424 may be implemented as a surface acoustic wave (SAW) filter.Additionally or alternatively, BPF 424 may be implemented using avariety of electronic circuit elements (e.g., one or more resistors,inductors, capacitors, and/or operational amplifiers, etc.).

When transmit/receive module 410 is operated in the receive mode,controller 436 (which itself may be controlled by the BSC) causestransmit/receive switches 426 and 432 to switch to provide a signal pathfrom antenna 412 to the RF summing junction through BPF 424, low noiseamplifier 428, and phase shifter 434. BPF 424 filters out components ofthe signal received by antenna 412 that are outside of the frequencyband(s) in which antenna element 400 is configured to receive signals.Low noise amplifier 428 then amplifies the received signal. After thesignal has been amplified, phase shifter 434 applies a phase shift tothe signal and passes the phase shifted signal to the RF summingjunction, where, for example, it is combined with signals from otherantenna elements (not shown) of the wireless communication terminal.

The phase shifts applied by phase shifter 434 to signals transmittedand/or received by antenna element 400 are controlled by controller 436,which in turn is controlled by the BSC. In this manner, the BSC controlsthe phase shifts applied by all of the antenna elements of the wirelesscommunication terminal in order to steer the main beam(s) of the antennaarray to different positions. In certain implementations, phase shifter434 may change the phase shift applied to a signal by changing thelength of the transmission line across which the signal travels.

With reference to FIG. 5, a beam steering controller 550 from a wirelesscommunication terminal (not shown) having an array of antenna elements(e.g., a phased array antenna) (not shown) is illustrated in accordancewith a non-limiting implementation of the present disclosure. BSC 550may correspond to BSC 36 illustrated in FIG. 1 or BSC 316 illustrated inFIG. 3 and/or be connected to transmit/receive module 410 illustrated inFIG. 4.

BSC 550 includes BSC circuitry 560, a multiplexer 562, and multiple beampointing tables 564(1)-(N) and is connected to the transmit/receivemodules (not shown) of the antenna elements of the wirelesscommunication terminal. Among other functions, BSC 550 is configured tocontrol individual antenna elements to steer the main beam(s) of theantenna array in a number of predetermined directions. In particular,BSC 550 may set the phase shifts (e.g., complex weights) to be appliedby the phase shifters of the transmit/receive modules of individualantenna elements to signals transmitted and/or received by the antennaelements in order to steer the main beam(s) of the antenna array in anumber of predetermined directions. In certain implementations, BSC maybe implemented as a microprocessor or another form of digital logiccircuitry.

Different beam pointing tables 564(1)-(N) correspond to differentcombinations of enabled and disabled elements of the antenna array. Theantenna array may include some number, m, antenna elements. Over time,one or more of those m antenna elements may fail and, as describedabove, be disabled. Therefore, the beam pointing tables 564(1)-(N) storevalues representing the phase shifts to be applied by different antennaelements depending on the particular combination of antenna elementsthat actually are enabled and disabled. For example, beam pointing table564(1) may store values representing the phase shifts to be applied byall of the antenna elements in order to steer the main beam(s) of theantenna array in each of a number of predetermined directions while allm antenna elements remain enabled. Similarly, beam pointing table 564(2)may store values representing the phase shifts to be applied by theenabled antenna elements to steer the main beam(s) of the antenna arrayin each of a number of predetermined directions when one of the antennaelements has been disabled and some configuration of m−1 antennaelements remain enabled, and so on and so forth. In someimplementations, BSC 550 may maintain beam pointing tables 564(1)-564(N)for every possible combination of enabled and disabled antenna elements.In other implementations, BSC 550 may maintain beam pointing tables564(1)-564(N) for only some limited subset of the possible combinationsof enabled and disabled antenna elements.

BSC circuitry 560 is configured to determine which antenna elements fromthe antenna array currently are enabled and to select, using multiplexer562, the particular beam pointing table from among the multiple beampointing tables 564(1)-564(N) that corresponds to the particularcombination of currently enabled and disabled antenna elements. BSCcircuitry 560 then accesses the phase shift values for the currentlyenabled antenna elements stored in the selected beam pointing table anduses the accessed phased shift values to control the phase shiftsapplied by the transmit/receive modules of the enabled antenna elementsto steer the main beam(s) of the antenna array in a number ofpredetermined directions.

In certain implementations, a calibration process may be performed(e.g., during manufacture, shortly after installation/initial use,and/or at different intervals following installation/initial use) todetermine the phase shifts to be applied by the antenna elements tosteer the main beam(s) of the antenna in a number of differentdirections for each of various different combinations of enabled anddisabled antenna elements. Values representing these phase shifts thenmay be stored in beam pointing tables corresponding to the differentcombinations of enabled and disabled antenna elements.

For example, in a wireless communication terminal with an antenna arrayhaving three antenna elements, x, y, and z, a calibration process may beperformed to determine phase shifts to be applied by individual antennaelements to steer the main beam(s) of the antenna array in a number ofdifferent directions for each possible combination of enabled anddisabled antenna elements. Corresponding beam pointing tables then maybe populated with phase shift values for each possible combination ofenabled and disabled antenna elements. In particular, in this example,beam pointing tables corresponding to the following possiblecombinations of enabled and disabled antenna elements may be populatedwith phase shift values determined during the calibration process:

-   -   (1) antenna elements x, y and z all enabled;    -   (2) antenna element x disabled and antenna elements y and z        enabled;    -   (3) antenna elements x and y disabled and antenna element z        enabled;    -   (4) antenna elements x and z disabled and antenna element y        enabled;    -   (5) antenna element y disabled and antenna elements x and z        enabled;    -   (6) antenna elements y and z disabled and antenna element x        enabled; and    -   (7) antenna element z disabled and antenna elements x and y        enabled.

In certain implementations, different beam pointing tables may be useddepending on whether the wireless communication terminal is transmittingor receiving. For example, a first set of beam pointing tables may storevalues representing the phase shifts to be applied by different antennaelements depending on the particular combination of antenna elementsthat actually are enabled and disabled when the wireless communicationterminal is transmitting and a second set of beam pointing tables maystore values representing the phase shifts to be applied by differentantenna elements depending on the particular combination of antennaelements that actually are enabled and disabled when the wirelesscommunication terminal is receiving. Such implementations may beemployed when the wireless communication terminal is configured toenable individual antenna elements to be disabled from transmitting butnot receiving and vice versa.

Although the beam pointing tables generally have been described above asbeing implemented as individual tables corresponding to particularcombinations of enabled and disabled antenna elements, the informationstored in the beam pointing tables also may be stored in a single tableand/or in a variety of other data structures or configurations.

In certain implementations, the wireless communication terminal may beconfigured to be able to communicate (e.g., transmit and/or receivesignals) using a variety of different modulation schemes (e.g.,different signal constellations). For example, in one particularimplementation, the wireless communication terminal may be configured tocommunicate using any of 16APSK, 8PSK, and QPSK. Use of 16APSK mayenable greater data transfer rates than use of 8PSK or QPSK, but 16APSKalso may require a higher signal-to-noise ratio than 8PSK or QPSK.Similarly, use of 8PSK may enable greater data transfer rates than useof QPSK, but 8PSK also may require a high signal-to-noise ratio thanQPSK. Consequently, as individual antenna elements fail and the overallgain of the antenna array decreases as a result, the wirelesscommunication terminal may not be capable of achieving thesignal-to-noise ratio necessary to enable use of a higher data ratemodulation scheme. Therefore, in addition to adjusting the phase shiftsto be applied by individual antenna elements to accommodate the failureof one or more antenna elements, the wireless communication terminalalso may adjust the modulation scheme used as antenna elements fail inorder to accommodate the failed antenna element(s) (e.g., based on adetermination that the remaining enabled antenna elements are incapableof providing the signal-to-noise ratio needed to support the currentmodulation scheme).

Additionally or alternatively, in certain implementations, when anantenna element fails, the wireless communication terminal may becapable of detecting the particular component(s) of the antenna elementthat failed. In such implementations, if the power amplifier or someother element along the transmit path of an antenna element fails butthe receive path of the antenna element remains operational, thewireless communication terminal may disable the antenna element fromtransmitting signals while still enabling the antenna element to receivesignals. In such cases, when the wireless communication terminal istransmitting signals, the wireless communication terminal may select abeam pointing table that corresponds to the combination of antennaelements currently enabled and disabled for transmitting signals and,when the wireless communication terminal is receiving signals, thewireless communication terminal may select a different beam pointingtable that corresponds to the combination of antenna elements currentlyenabled and disabled for receiving signals.

The teachings of the present disclosure may be applicable to anywireless communication terminal having an antenna array with multipleantenna elements and may enable such a wireless communication terminalto continue communicating (e.g., transmitting and/or receiving signals)notwithstanding a failure of one or more of the antenna elements of theantenna array. Although specific examples described above may bedescribed in the context of mobile satellite communication terminals,the teachings of the present disclosure are more broadly applicable andmay be employed in any type of wireless communication terminal having anantenna array with multiple antenna elements.

Aspects of the present disclosure may be implemented entirely inhardware, entirely in software (including firmware, resident software,micro-code, etc.) or in combinations of software and hardware that mayall generally be referred to herein as a “circuit,” “module,”“component,” or “system.” Furthermore, aspects of the present disclosuremay take the form of a computer program product embodied in one or morecomputer-readable media having computer-readable program code embodiedthereon.

Any combination of one or more computer-readable media may be utilized.The computer-readable media may be a computer-readable signal medium ora computer-readable storage medium. A computer-readable storage mediummay be, for example, but not limited to, an electronic, magnetic,optical, electromagnetic, or semiconductor system, apparatus, or device,or any suitable combination of the foregoing. More specific examples (anon-exhaustive list) of such a computer-readable storage medium includethe following: a portable computer diskette, a hard disk, a randomaccess memory (RAM), a read-only memory (ROM), an erasable programmableread-only memory (EPROM or Flash memory), an appropriate optical fiberwith a repeater, a portable compact disc read-only memory (CD-ROM), anoptical storage device, a magnetic storage device, or any suitablecombination of the foregoing. In the context of this document, acomputer-readable storage medium may be any tangible medium that cancontain or store a program for use by or in connection with aninstruction execution system, apparatus, or device.

A computer-readable signal medium may include a propagated data signalwith computer-readable program code embodied therein, for example, inbaseband or as part of a carrier wave. Such a propagated signal may takeany of a variety of forms, including, but not limited to,electro-magnetic, optical, or any suitable combination thereof. Acomputer-readable signal medium may be any computer-readable medium thatis not a computer-readable storage medium and that can communicate,propagate, or transport a program for use by or in connection with aninstruction execution system, apparatus, or device. Program codeembodied on a computer-readable signal medium may be transmitted usingany appropriate medium, including but not limited to wireless, wireline,optical fiber cable, RF, etc., or any suitable combination of theforegoing.

Computer program code for carrying out operations for aspects of thepresent disclosure may be written in any combination of one or moreprogramming languages, including object oriented programming languages,dynamic programming languages, and/or procedural programming languages.

The flowchart and block diagrams in the figures illustrate examples ofthe architecture, functionality, and operation of possibleimplementations of systems, methods and computer program productsaccording to various aspects of the present disclosure. In this regard,each block in the flowchart or block diagrams may represent a module,segment, or portion of code, which comprises one or more executableinstructions for implementing the specified logical function(s). Itshould also be noted that, in some alternative implementations, thefunctions noted in the block may occur out of the order illustrated inthe figure(s). For example, two blocks shown in succession may, in fact,be executed substantially concurrently, or the blocks may sometimes beexecuted in the reverse order, depending upon the functionalityinvolved. It will also be noted that each block of the block diagramsand/or flowchart illustration, and combinations of blocks in the blockdiagrams and/or flowchart illustration, can be implemented by specialpurpose hardware-based systems that perform the specified functions oracts, or combinations of special purpose hardware and computerinstructions.

The terminology used herein is for the purpose of describing particularaspects only and is not intended to be limiting of the disclosure. Asused herein, the singular forms “a”, “an” and “the” are intended toinclude the plural forms as well, unless the context clearly indicatesotherwise. It will be further understood that the terms “comprises”and/or “comprising,” when used in this specification, specify thepresence of stated features, integers, steps, operations, elements,and/or components, but do not preclude the presence or addition of oneor more other features, integers, steps, operations, elements,components, and/or groups thereof.

The corresponding structures, materials, acts, and equivalents of anymeans or step plus function elements in the claims below are intended toinclude any disclosed structure, material, or act for performing thefunction in combination with other claimed elements as specificallyclaimed. The description of the present disclosure has been presentedfor purposes of illustration and description, but is not intended to beexhaustive or limited to the disclosure in the form disclosed. Manymodifications and variations will be apparent to those of ordinary skillin the art without departing from the scope and spirit of thedisclosure. The aspects of the disclosure herein were chosen anddescribed in order to explain the principles of the disclosure and thepractical application, and to enable others of ordinary skill in the artto understand the disclosure with various modifications as are suited tothe particular use contemplated.

What is claimed is:
 1. A wireless communications terminal, comprising: an antenna array having a plurality of antenna elements, each of which is configured to apply a phase shift to a signal transmitted by the antenna element; and a beam steering controller configured to: steer a main beam of the antenna by controlling the phase shifts applied by the antenna elements, detect a failure of an antenna element, and in response to detecting the failure of the antenna element: disable the failed antenna element, and modify the phase shifts applied by remaining ones of the antenna elements.
 2. The wireless communications terminal of claim 1, further comprising a memory storing a beam pointing data structure storing values indicative of different phase shifts to be applied by corresponding antenna elements to steer the main beam of the antenna in each of multiple different predetermined directions, wherein the beam steering controller is configured to control the phase shifts applied by the antenna elements by reading values indicative of phase shifts to be applied from the beam pointing data structure.
 3. The wireless communications terminal of claim 2, wherein: the memory further stores an alternative beam pointing data structure storing values indicative of different phase shifts to be applied by corresponding remaining antenna elements to steer the main beam of the antenna in at least some of the multiple predetermined directions; and the beam steering controller is configured to modify the phase shifts applied by the remaining antenna elements by reading values indicative of phase shifts to be applied from the alternative beam pointing table.
 4. The wireless communications terminal of claim 1, wherein the beam steering controller is configured to disable the failed antenna element by applying a predetermined impedance to the failed antenna element.
 5. The wireless communications terminal of claim 1, wherein each antenna element includes a power amplifier configured to amplify the signal transmitted by the antenna element.
 6. The wireless communications terminal of claim 5, wherein the beam steering controller is configured to detect the failure of the antenna element by detecting the failure of the power amplifier in the failed antenna element.
 7. The wireless communications terminal of claim 1, wherein each antenna element is further configured to apply a phase shift to a signal received by the antenna element.
 8. The wireless communications terminal of claim 1, wherein the wireless communication terminal is configured to: modulate signals transmitted by the antenna using at least one of a first signal constellation and a second signal constellation; and switch from using the first signal constellation to modulate signals prior to detecting the failure of the failed antenna element to using the second signal constellation to modulate signals in response to detecting the failure of the failed antenna element.
 9. The wireless communications terminal of claim 8, wherein the second signal constellation is less sensitive to noise than the first signal constellation.
 10. A method of operating a phased array antenna that includes multiple antenna elements, the method comprising: controlling phase shifts applied by individual ones of the antenna elements to steer a main beam of the antenna in a direction; determining that one of the antenna elements has failed; and in response to determining that the antenna element has failed: disabling the failed antenna element, and modifying the phase shifts applied by remaining ones of the antenna elements to steer the main beam of the antenna effectively in the same direction.
 11. The method of claim 10, wherein controlling phase shifts applied by individual ones of the antenna elements to steer a main beam of the antenna in a direction includes reading the phase shifts to be applied to the individual antenna elements from a first beam pointing table.
 12. The method of claim 11, wherein modifying the phase shifts applied by remaining ones of the antenna elements to steer the main beam of the antenna effectively in the same direction includes reading the modified offsets to be applied by remaining ones of the antenna elements from a second beam pointing table that is different from the first beam pointing table.
 13. The method of claim 10, wherein disabling the failed antenna element includes applying a predetermined impedance to the failed antenna element.
 14. The method of claim 10, further comprising: amplifying signals transmitted by individual ones of the antenna elements using power amplifiers incorporated within the individual antenna elements.
 15. The method of claim 14, wherein determining that the antenna element has failed includes determining that the power amplifier included in the failed antenna element has failed.
 16. The method of claim 10, further comprising: using a first signal constellation to modulate signals transmitted by the antenna prior to determining that the antenna element has failed; and in response to determining that the antenna element has failed, using a second signal constellation that is different from the first signal constellation to modulate signals transmitted by the antenna.
 17. The method of claim 16, wherein using a second signal constellation that is different from the first signal constellation to modulate signals transmitted by the antenna includes using a second signal constellation that is less sensitive to noise than the first signal constellation to modulate signals transmitted by the antenna.
 18. A wireless communication terminal, comprising: a phased array antenna having multiple antenna elements; memory storing multiple different beam pointing data structures, each beam pointing data structure: corresponding to a particular combination of enabled and disabled antenna elements of the antenna, and storing values representing phase shifts to be applied by individual ones of the enabled antenna elements for the particular combination to steer the main beam of the antenna in a number of different predetermined directions; and a beam steering controller configured to: determine a current combination of enabled and disabled antenna elements, select a beam pointing data structure from among the multiple different beam pointing data structures that corresponds to the current combination of enabled and disabled antenna elements, and control phase shifts applied by the currently enabled antenna elements to steer the main beam of the antenna using phase shifts represented in the selected beam pointing data structure.
 19. The wireless communication terminal of claim 18, wherein the wireless communication terminal is configured to: modulate signals transmitted by the antenna using multiple different modulation techniques, individual ones of the modulation techniques having different sensitivities to noise; and select a particular one of the modulation techniques to use to modulate signals transmitted by the antenna based on the current combination of enabled and disabled antenna elements.
 20. The wireless communication terminal of claim 18, wherein: each antenna element is configured to operate in at least one of a transmit mode for transmitting a signal and a receive mode for receiving a signal; each antenna element includes a power amplifier for amplifying a signal transmitted by the antenna element when the antenna element is operating in the transmit mode; the wireless communication terminal is configured to: operate in at least one of a transmitting mode for transmitting signals from the antenna and a receiving mode for receiving signals with the antenna, control individual antenna elements to operate in their transmit modes when the wireless communication terminal is operating in the transmitting mode, control individual antenna elements to operate in their receive modes when the wireless communication terminal is operating in the receiving mode, detect that a power amplifier of an antenna element has failed, and disable an antenna element from operating in the transmit mode as a consequence of detecting that the power amplifier of the antenna element has failed; the beam steering controller is configured to determine a current combination of enabled and disabled antenna elements by detecting a first current combination of enabled and disabled antenna elements for operating in the transmit mode when the wireless communication terminal is operating in the transmitting mode and a second combination of enabled and disabled antenna elements for operating in the receive mode when the wireless communication terminal is operating in the receiving mode; and the beam steering controller is configured to select a beam pointing data structure from among the multiple different beam pointing data structures that corresponds to the current combination of enabled and disabled antenna elements by selecting a transmitting beam pointing data structure that corresponds to the first current combination of enabled and disabled antenna elements when the wireless communication terminal is operating in the transmitting mode and by selecting a receiving beam pointing data structure that corresponds to the second current combination of enabled and disabled antenna elements when the wireless communication terminal is operating in the receiving mode. 